1. Field of the Invention
The present invention relates to a method and apparatus for controlling a continuously variable V-belt transmission.
2. Description of the Prior Art
A conventional method for controlling a continuously variable transmission, is disclosed in laid-open Japanese utility model application No. Sho 55-138137, which also describes a control apparatus as shown in FIG. 1.
Power fron an engine 201 is transmitted via a continuously variable transmission 202 to wheels 203. A fuel control lever 204 of the engine 201 is actuated by a servo motor 205, a shift lever 206 is actuated by a servo motor 207 and a brake 208 is actuated by a servo motor 209. The servo motors 205, 207 and 209 are controlled by command signals 211, 212 and 213, respectively, from a speed control unit 210, and their position detecting signals 214, 215 and 216 are fed back to the speed control unit 210. The engine 201 is provided with an engine sensor 217 with which an oil temperature of the engine 201 and a vibration thereof are detected and signals 218 representing this information is fed to the speed control unit 201. The continuously variable transmission 202 is provided with a transmission sensor 219 with which an oil pressure of the continously variable transmission 202, an oil temperature thereof and an oil amount thereof are detected and signals representing this information is fed to the speed control unit 210. An input revolution speed to the continuously variable transmission 202 and an output revolution speed thereof are detected by revolution speed sensors 221 and 222, respectively, and signals 223 and 224 representing this information is fed to the speed control unit 210. Also fed to the speed control unit 210 is a signal 226 produced by a shift command lever 225 which is manipulated by a driver. The speed control unit 210 stores a plurality of patterns of actions of the engine 201, continuously variable transmission 202 and brake 208 and also stores the optimum conditions of oil temperature and vibration of the engine 201 and the optimum conditions of oil pressure, oil temperature and oil amount of the continuously variable transmission 202, and it actuates the servo motors 205, 207 and 209 dependent upon the information stored therein and those signals generated by the above mentioned sensors so as to effect a shift control.
The conventional control method of this kind requires a considerable numbers of sensors, such as a position detecting sensor for each of the respective servo motors, an input and output rotational speed sensor, an engine sensor and a transmission sensor, thus requiring a very expensive control apparatus to carry out this method, another problem is that since the conventional sped control unit stores a plurality of patterns of actions, the control becomes necessarily complicated, thus inviting trouble, malfunction and the like.